The present invention relates generally to key detection structures for wind instruments, and more particularly to an improved key detection structure for a wind instrument which allows detector units, for detecting states etc. of corresponding keys, to be readily attached and detached to and from the wind instrument.
There have been known key detection structures of a type which reproduces electronic tones by detecting operation of keys on a wind instrument, and examples of such a type of key detection structure are disclosed in Japanese Utility Model Application Laid-open Publication No. HEI-4-89999 and Japanese Patent Application Laid-open Publication No. HEI-8-305362. According to the disclosure of the No. HEI-4-89999 and No. HEI-8-305362 publications, a module including switches and hall elements is previously incorporated in a tubular body and keys forming the wind instrument. Namely, the wind musical instruments disclosed in these publications differ in construction and tone-generating form from the so-called acoustic type wind musical instruments; namely, if the module is removed, the disclosed wind musical instruments can no longer generate any performance tone. I recent years, however, there has been a demand that the above-mentioned module be detachably attached to an acoustic musical instrument so that two different kinds of tones, i.e. electronic reproduced tone and acoustic performance tone generated by the musical instrument itself, can be used appropriately as needed.
Where an acoustic-type wind musical instrument is to be constructed to detect operation of keys in order to reproduce electronic tones as well, use of structure (1) and structure (2) outlined below are conceivable.
According to structure (1), a magnetic member is fixed to a position adjacent to the reverse or back surface of a key, and a hall element is mounted in the tubular body. As the key opens or closes a tone hole, variation in magnetic field responsive to the displacement of the magnetic member is detected by the corresponding hall element, so that an electrical signal corresponding to the key's opening or closing movement is output.
Structure (2) is different from structure (1) in terms of attached positions of the magnetic member and hall element. Namely, according to structure (2), the magnetic member is supported outside the corresponding key via an arm, while the hall element is attached to the outer surface of the tubular body.
However, structure (1) above would present the inconvenience that operation for attaching the magnetic member to the position adjacent to the back surface of the key requires is very cumbersome and requires a great amount of time. The inconvenience is due to the fact that, during the attaching operation, it is essential to attach the magnetic member after detaching or disassembling the key from the tubular body and insert the magnetic member into a narrow space between the tubular body and the key. Further, because the magnetic member is attached to the position adjacent to the back surface of the key, the structure would be subjected to the constraint that the tone hole can not be opened and closed by the key unless the magnetic member is sized so to be received in the tone hole.
Further, structure (2) above would present the inconveniences that operation for attaching the hall element to the outer peripheral surface of the tubular body and a construction for supporting the magnetic member via the arm tend to be very complicated, and that operation for disassembling the key and the like at the time of repair or care of the wind instrument tends to be cumbersome and difficult. In particular, because the outer peripheral surface of the tubular body is a curved surface, the attached state of the hall element tends to be unstable.